Liquid display

ABSTRACT

A printed layer having opening portions is provided at a position opposite to an observer of a liquid crystal display device, a display is performed by use of absorption or chromaticity of the printed layer when an external light source is utilized, and a display is performed by transmitting light through the opening portions of the printed layer when an auxiliary light source is turned on, and further different voltages between when the external light source is utilized and when the auxiliary light source is used are applied to a liquid crystal layer by a gradation reversal circuit. Moreover, reversal of brightness and darkness of a display by the use of the external light source and the auxiliary light source is eliminated by a polarizing film or a cholesteric liquid crystal polymer film disposed on the rear face of the liquid crystal display device, thereby enabling a liquid crystal display device with excellent visibility.

TECHNICAL FIELD

The present invention relates to a liquid crystal display device, morespecifically, to a liquid crystal display device for performing a brightdisplay using a reflection-type polarizing film by its reflectioncharacteristic, or performing a display using a selective-reflectiontype film by its difference in color tones.

BACKGROUND TECHNOLOGY

Recently, a reflection-type liquid crystal display device for performinga display by an external light source has been developed as a liquidcrystal display device for portable information processing devices, andimprovement of brightness and multi-color display has progressed. As amethod for improving brightness, a method is tried in which areflection-type polarizing film is provided on the side of a liquidcrystal cell opposite to the visible side, and a printed layer is formedon the rear face of the reflection-type polarizing film. Thereflection-type polarizing film has a transmission axis and a reflectionaxis as two optical axes orthogonal to each other and hascharacteristics for transmitting a light linearly polarized in thedirection parallel to the transmission axis but for reflecting anincident light linearly polarized in the direction parallel to thereflection axis.

Moreover, as another method for improving brightness of the liquidcrystal display device, a method using a selective-reflectioncharacteristic of a cholesteric liquid crystal polymer is alsoconsidered.

The polarizing film conventionally and widely used in a liquid crystaldisplay panel is an absorption-type polarizing film. The absorption-typepolarizing film has two optical axes, a transmission axis and anabsorption axis, orthogonal to each other, and it has characteristicsfor transmitting a light linearly polarized in the direction parallel tothe transmission axis but for absorbing an incident light linearlypolarized in the direction parallel to the absorption axis.

Therefore, the absorption-type polarizing film is used in combinationwith the aforesaid reflection-type polarizing film, whereby the liquidcrystal display device has a large transmission characteristic when thetransmission axes of the polarizing films are parallel to each other anda large reflection characteristic when the transmission axes areorthogonal to each other.

Accordingly, the liquid crystal display device has a large absorptioncharacteristic (a black display) when the two absorption-type polarizingfilms are disposed in such a manner that the transmission axes thereofare orthogonal to each other, different from a transmissioncharacteristic when they are disposed in such a manner that thetransmission axes are parallel to each other.

In the case of the liquid crystal display device using twoabsorption-type polarizing films, a reflector is disposed on the rearface side of the absorption-type polarizing film disposed on the sideopposite to the visible side in relation to the liquid crystal cell,whereby a bright display is performed by reflecting incident light fromthe external light source to the visible side in a transmission stateand a dark display is performed in an absorption state. In this case,however, since the reflected light which is viewed passes through theabsorption-type polarizing film positioned on the reflector twice, thelight is absorbed partly, resulting in a display of which brightnesssomewhat decreases.

Moreover, the reflector having light scattering properties is used,absorption by the absorption-type polarizing film occurs due toinstability in polarization by the reflector, whereby brightness be comeimpaired.

Furthermore, in a dark environment without an external light source,since the visibility of the display of the liquid crystal display deviceextremely deteriorates, an auxiliary light source is provided in theliquid crystal display device in many cases. In that case, a reflectorof a transflective-type is used in place of the reflector without atransmission characteristic.

In this case, the bright display by reflection of an incident light fromthe external light source, briefly explained except for the liquidcrystal layer, corresponds to the case where the transmission axes ofthe two absorption-type polarizing films are parallel to each other,resulting in a bright display also in the case where the auxiliary lightsource is used. The converse dark display corresponds to the case wherethe transmission axes of the two absorption-type polarizing films areorthogonal to each other, resulting in a bright display also in the casewhere the auxiliary light source is used.

In contrast to the above, according to the liquid crystal display deviceusing an absorption-type polarizing film and a reflection-typepolarizing film in combination, in the case where the external lightsource is used, a bright state is a state where the transmission axis ofthe absorption-type polarizing film and the reflection axis of thereflection-type polarizing film are parallel to each other to obtain areflection characteristic of the reflection-type polarizing film.Accordingly, the reflection-type polarizing film itself reflectsincident light resulting in a bright display. Conversely, a dark stateis a state where the transmission axis of the absorption-type polarizingfilm and the transmission axis of the reflection-type polarizing filmare parallel to each other and uses the transmission characteristic, andthus it is required to dispose or print a light absorbing material onthe rear face of the reflection-type polarizing film. As above, brightand dark displays with excellent contrast can be performed by means ofthe liquid crystal display device using the absorption-type polarizingfilm and the reflection-type polarizing film.

The structure of the conventional liquid crystal display panel of theliquid crystal display device as above is explained with reference tothe drawings. FIG. 16 is a plane view showing a plane structure of theprincipal portion thereof, and FIG. 17 is a partly enlarged sectionalview along the A—A line in FIG. 16.

In the liquid crystal display panel, a first substrate 1 and a secondsubstrate 5 made of a transparent material such as glass or the like areoppositely disposed to each other, a predetermined gap between them iskept by a spacer not shown, peripheries of the substrates are bondedtogether by a sealant 4 serving as an adhesive, and a liquid crystallayer 8 is filled in the gap and sealed by an end-sealing material 26.

M pieces of scanning electrodes 2 made of a transparent electrode filmare formed on the inner face of the first substrate 1, N pieces of dataelectrodes 6 intersecting the scanning electrodes 2 are formed on theinner face of the second substrate 5, and intersections of the scanningelectrodes 2 and the data electrodes 6 form pixel portions 21 to form aliquid crystal cell of a matrix type liquid crystal display panel havingan M×N piece of pixel portions.

In FIG. 16, since the second substrate 5 positioned on the uppermostside of this liquid crystal cell is transparent, the data electrodes 6,the first substrate 1 and the scanning electrodes 2, the sealant 4, theend-sealing material 26, and the like positioned thereunder are allshown by solid lines.

In the above liquid crystal display panel, there is a liquid crystaldisplay panel of an active-matrix type having a switching element ineach pixel portion 21 and a liquid crystal display panel of apassive-matrix type without providing a switching element, and theliquid crystal display panel as the passive-matrix type is explainedhere.

It should be noted that, as shown in FIG. 17, an alignment layer 3 andan alignment layer 7 are formed on the inner face of the first substrate1 and the scanning electrodes 2 and on the inner face of the secondsubstrate 5 and the data electrodes 6 respectively in order to align theliquid crystal molecules of the liquid crystal layer 8 regularly.

Moreover, a first polarizing film 11 is disposed on the rear face sideof the first substrate 1, which is the side opposite to the observer'sside (the visible side: the upper side in FIG. 17) of the liquid crystalcell, and a second polarizing film 12 is disposed on the front face sideof the second substrate which is the observer's side.

The first polarizing film 11 is a reflection-type polarizing film and,for example, DBEF (trade name) manufactured by Sumitomo 3M Ltd. is used,and the second polarizing film 12 is an absorption-type polarizing film.On the rear face of the first polarizing film 11, a printed layer 13 ofblack ink is provided as a light absorbing layer.

The first polarizing film 11 and the second polarizing film 12 aredisposed in such a manner that the respective transmission axes areorthogonal to each other, and for the liquid crystal layer 8, used istwisted nematic liquid crystal is used for optically rotating passinglight about 90 degrees between the first substrate 1 and the secondsubstrate 5.

Therefore, when the environment is bright where this liquid crystaldisplay panel is used, external light is incident from the front faceside of the second substrate 5. Therefore, in a pixel portion forperforming a dark display, a first incident ray of light L1 passesthrough the second polarizing film 12 to become a linearly polarizedlight, and is optically rotated 90° by the liquid crystal layer 8 and isincident to the reflection-type polarizing film which is the firstpolarizing film 11 as a light linearly polarized in the directionparallel to the transmission axis thereof, so that the light passesthrough the first polarizing film 11 and is absorbed by the printedlayer 13 on the rear face thereof.

Moreover, as for a bright display, a second incident light L2 passesthrough the second polarizing film 12 to become a linearly polarizedlight, optical rotatory of the liquid crystal layer 8 is lost byapplying a large voltage to the liquid crystal layer 8, the incidentlight into the liquid crystal layer passes through without beingoptically rotated and is incident to the reflection-type polarizing filmwhich is the first polarizing film 11 as a light linearly polarized inthe direction parallel to the reflection axis thereof, so that the lightis reflected by the reflection-type polarizing film 11 to become astrong reflected light L3 and passes through the liquid crystal layer 8and the second polarizing film 12 to emit to the visible side.

As above, this liquid crystal display panel performs the dark display bya linearly polarized light being incident to the transmission axis ofthe reflection-type polarizing film and an absorption characteristic ofthe printed layer 13 and enables the bright display by a reflectioncharacteristic of the reflection-type polarizing film.

However, since the printed layer 13 provided on the first polarizingfilm 11 which is the reflection-type polarizing film does not have atransmission characteristic, even if an auxiliary light source isdisposed on the rear face side of the reflection-type polarizing film11, light from the auxiliary light source is absorbed by the printedlayer 13 having the absorption characteristic and hence light does notreach the visible side.

If a display is performed using the auxiliary light source withoutproviding the printed layer 13, the bright display using incident lightby the external light source becomes a dark display in the display bythe auxiliary light source, and conversely, the dark display usingincident light by the external light source becomes a bright display inthe display by the auxiliary light source. Consequently, brightness anddarkness be come reversed between in the reflection-type display usingthe external light source and in the transmission-type display using theauxiliary light source.

As described above, in the case where the auxiliary light source is usedin a dark environment, in the conventional liquid crystal display panelin which a light absorbing layer is provided on the rear face of thereflection-type polarizing film, transmittance of light which theauxiliary light source emits is considerably poor, and thus a displaycan not be performed. Even when the printed layer is removed to applylight of the auxiliary light source to the visible side, a state where adark display is performed in the reflection-type display becomes a statewhere the transmittance is large due to the combination of theabsorption-type polarizing film and the reflection-type polarizing film,whereby light of the auxiliary light source passes resulting in a brightdisplay, that is, the display in which brightness and darkness thereofis reversed.

Similarly, a state where a bright display is performed in thereflection-type display becomes a state where the transmittance is smallbecause the transmission axis of the absorption-type polarizing film andthe transmission axis of the reflection-type polarizing film areorthogonal to each other, whereby light of the auxiliary light source isshut out resulting in a dark display, that is, the display in whichbrightness and darkness thereof is reversed.

Further, also in the case where a cholesteric liquid crystal polymer isused in place of the reflection-type polarizing film, the display modethereof becomes nearly the same as in the case where the reflection-typepolarizing film is used.

More specifically, the cholesteric liquid crystal polymer selectivelyand largely reflects (selective reflection) light within a predeterminedwavelength region out of the visible light and transmits light withinthe other wavelength region. Accordingly, the cholesteric liquid crystalpolymer has a large reflection characteristic to the external lightsource within a wavelength region of the selective reflection and atransmission characteristic within the other wavelength region.Therefore, the bright display is performed using the selectivereflection of the cholesteric liquid crystal polymer and the darkdisplay is performed by an absorbing material disposed on the rear faceside of the cholesteric liquid crystal polymer.

In the case where the auxiliary light source is turned on, light is shutout within the wavelength region of the selective reflection, resultingin a dark display and light of the auxiliary light source is transmittedwithin the other wavelength region resulting in a bright display.Accordingly, brightness and darkness of the display are reversed.

As described above, in the case of a conventional translucent-type(transflective) liquid crystal display device using the reflection-typepolarizing film and having the auxiliary light source, the display comesto one in which the bright display in the reflection display by theexternal light source and the bright display in the transmission displayby turning on the auxiliary light source are reversed. Moreover, sincethe printed layer provided on the rear face of the reflection-typepolarizing film prevents light from the auxiliary light source fromtransmitting, it is difficult to concurrently use the transmissiondisplay by the auxiliary light source.

Also in the case where the cholesteric liquid crystal polymer is used asa reflector, in the transflective liquid crystal display device havingthe auxiliary light source, the display comes to one in which the brightdisplay in the reflection display and the bright display in thetransmission display by turning on the auxiliary light source arereversed. Furthermore, there is a disadvantage that when the printedlayer is provided on the rear face of the cholesteric liquid crystalpolymer, light by the auxiliary light source can not be transmitted.

DISCLOSURE OF THE INVENTION

The present invention is made to solve the aforesaid disadvantage, andits object is to make it possible to use emitted light of an auxiliarylight source efficiently and to prevent brightness and darkness of adisplay from being reversed between a reflection display by an externallight source and a transmission display by use of the auxiliary lightsource, thereby realizing a display always with high brightness andexcellent visibility, in a liquid crystal display device using areflection-type polarizing film or a cholesteric liquid crystal polymerfilm.

To achieve the above object, the present invention provides a liquidcrystal display device structured as follows.

A liquid crystal display device of the present invention comprises aliquid crystal cell made by disposing a first substrate provided withscanning electrodes and a second substrate provided with data electrodesin such a manner that the scanning electrodes and the data electrodesare oppositely disposed to each other with a predetermined gaptherebetween, and a liquid crystal layer being filled between the firstsubstrate and the second substrate.

Moreover, the second substrate of the liquid crystal cell is disposed onthe visible side, a polarizing film is disposed on the side of each faceof the first substrate and the second substrate opposite to the facecontacting the liquid crystal layer, the polarizing film disposed on thefirst substrate side is a reflection-type polarizing film, an auxiliarylight source is provided on the side of the reflection-type polarizingfilm opposite to the face on the first substrate side, and a lightabsorbing layer for transmitting part of light is provided between thereflection-type polarizing film and the auxiliary light source.

Furthermore, means for varying a voltage applied to the liquid crystallayer between the auxiliary light source being turned on and beingturned off is provided.

It is preferable that the above means is a circuit for reversing agradation signal applied to the liquid crystal layer between theauxiliary light source being turned on and being turned off.

Moreover, it is preferable to provide a scattering film having lightscattering properties between the reflection-type polarizing film andthe light absorbing layer.

It is possible to provide the scattering film adhering to thereflection-type polarizing film.

Furthermore, as the scattering film, it is also possible to bond aplastic film in which asperities are formed on the front face thereof ora plastic film in which beads with different refractive indexes aredispersed to the rear face of the reflection-type polarizing film withan adhesive.

It is preferable to provide a gap between the scattering film and thelight absorbing layer.

The light absorbing layer can be made of a printed layer having openingportions with a large transmittance and absorbing portions with a smalltransmittance.

It is desirable that the light absorbing layer has a plurality ofopening portions or portions having a transmission characteristic at apixel portion.

It is preferable that the light absorbing layer having the openingportions has a grid form in which the opening portions and the absorbingportions are arranged regularly and the printed layer forming theabsorbing portions is made of a thick film for absorbing external lightby the thickness thereof when an incident angle of the external lightbecomes large.

The light absorbing layer may have a plurality of opening portionshaving different transmittances, or the light absorbing layer may bemade so that the light absorbing layer as a whole transmits part oflight. Alternatively, the light absorbing layer may be made of aplurality of absorbing portions having different spectralcharacteristics within a visible light region.

Alternatively, it is also possible that liquid crystal display deviceaccording to the present invention comprises the same liquid crystalcell as above, wherein the second substrate of the liquid crystal cellis disposed on the visible side, an absorption-type polarizing film isdisposed on the side of a face of the second substrate opposite to theface contacting the liquid crystal layer and a cholesteric liquidcrystal polymer film is disposed on the side of a face of the firstsubstrate opposite to the face contacting the liquid crystal layerrespectively, an auxiliary light source is disposed on the side of aface of the cholesteric liquid crystal polymer film opposite to the faceon the first substrate side with a light absorbing layer fortransmitting part of light therebetween, and means for varying a voltageapplied to the liquid crystal layer between while the auxiliary lightsource is turned on and while it is turned off is provided.

It is preferable that the above means in this case is also a circuit forreversing a gradation signal applied to the liquid crystal layer betweenwhile the auxiliary light source is turned on and while it is turnedoff.

In this liquid crystal display device, it is preferable that aretardation film is disposed between the second substrate and theabsorption-type polarizing film, and a ¼ λ (quarter-wavelength) film isdisposed between the first substrate and the cholesteric liquid crystalpolymer film respectively.

It is possible that the light absorbing layer is a printed layer havingtransparency so that the light absorbing layer as a whole transmits partof light.

Alternatively, the liquid crystal display according to the presentinvention comprises a liquid crystal cell made by disposing a firstsubstrate provided with scanning electrodes and a second substrateprovided with data electrodes in such a manner that the scanningelectrodes and the data electrodes are opposed to each other with apredetermined gap therebetween, a liquid crystal layer being filledbetween the first substrate and the second substrate, and a first colorfilter being provided on the first substrate or the second substrate, inwhich the second substrate of the liquid crystal cell is disposed on thevisible side.

Moreover, an absorption-type polarizing film is disposed on the side ofa face of the second substrate opposite to the face contacting theliquid crystal layer and a reflection-type polarizing film is disposedon the side of a face of the first substrate opposite to the facecontacting the liquid crystal layer respectively, an auxiliary lightsource is disposed on the side of a face of the reflection-typepolarizing film opposite to the face on the first substrate side with asecond color filter therebetween, and means for varying a voltageapplied to the liquid crystal layer between the auxiliary light sourcebeing turned on and being turned off is provided.

Moreover, it is preferable to provide a scattering film having lightscattering properties between the first substrate and the second colorfilter.

As the scattering film, it is possible to use a plastic film in whichasperities are formed on the front face thereof or a plastic film inwhich beads with different refractive indexes are dispersed.

It is preferable to use the first color filter and the second colorfilter respectively made of red, green and blue color filters.

It is preferable that the first color filter and the second color filterare provided on one face side of the first substrate and on the otherface side respectively and disposed in such a manner that the colorfilters of the same color overlap one another with the first substratetherebetween in almost the same areas.

It is also possible to provide means for controlling a voltage appliedto the liquid crystal layer of the liquid crystal cell to varybrightness of a display of a halftone in accordance with brightness ofan external environment.

OPERATION

The printed layer is provided directly on or across a medium such as afilm or the like on the rear face of the reflection-type polarizing filmused in the liquid crystal display device of the present invention. Theprinted layer is provided with the opening portions with a largetransmittance and the auxiliary light source is disposed on the rearface of the printed layer having the opening portions, whereby in anenvironment where the external light source as a main light source isbright (the reflection display), a bright display is performed by theuse of the reflective characteristic of the reflection-type polarizingfilm and a dark display is performed by absorption of the printed layer.In a dark environment (the transmission display), the auxiliary lightsource is turned on and light of the auxiliary light source is appliedto the observer's side through the opening portions provided in theprinted layer to perform a bright display. In this case, the gradationreversal circuit is switched between during ON and during OFF oflighting of the auxiliary light source on the circuit side, so that asmall voltage is applied to the liquid crystal layer in the transmissiondisplay at a pixel portion where a large voltage is applied to theliquid crystal layer in the reflection display. Conversely, in thereflection display, a large voltage is applied to the liquid crystallayer in the transmission display at a pixel portion where a smallvoltage is applied to the liquid crystal layer in the reflectiondisplay.

By the gradation reversal circuit, in the reflection display and thetransmission display, large on small voltages applied to the liquidcrystal layer are reversed and simultaneously a reversal of bright anddark displays occurs by the reflection-type polarizing film, so that thebright display in the reflection display becomes the bright display alsoin the transmission display in the liquid crystal display device.Especially, as for prevention of the reversal of the bright and darkdisplays of an image, since information of colors is changed between thereflection display and the transmission display due to the reversal ofthe bright and dark displays in a color liquid crystal display deviceusing a color filter or the like, the prevention of the reversal of thebright and dark displays is very effective.

Similarly to the above, in the case where the cholesteric liquid crystalpolymer film is used on the rear face side of the first substrate, theprinted layer is provided directly on or across a medium such as a filmon the rear face of the cholesteric liquid crystal polymer film, theprinted layer is provided with the opening portions with a largetransmittance, and the auxiliary light source is disposed on the rearface of the printed layer having the opening portions, whereby in abright environment (the reflection display), a bright display isperformed by use of the reflection characteristic of the reflection-typepolarizing film and a dark display is performed by absorption of theprinted layer. In a dark environment, (the transmission display), theauxiliary light source is turned on and light of the auxiliary lightsource is applied to the observer's side through the opening portionsprovided in the printed layer to perform a bright display. In this case,the gradation reversal circuit is switched between during ON and duringOFF of lighting of the auxiliary light source on the circuit side, sothat a small voltage is applied to the liquid crystal layer in thetransmission display at a pixel portion where a large voltage is appliedto the liquid crystal layer in the reflection display. Conversely, alarge voltage is applied to the liquid crystal layer in the transmissiondisplay at a pixel portion where a small voltage is applied to theliquid crystal layer in the reflection display.

By the gradation reversal circuit, in the reflection display and thetransmission display, large or small voltages applied to the liquidcrystal layer are reversed and simultaneously a reversal of bright anddark displays occurs by the cholesteric liquid crystal polymer film, sothat the bright display in the reflection display becomes the brightdisplay also in the transmission display in the liquid crystal displaydevice. Especially, as for prevention of the reversal of the bright anddark displays of an image, since information of colors is changedbetween the reflection display and the transmission display due to thereversal of the bright and dark displays in a color liquid crystaldisplay device using a color filter or the like, the prevention of thereversal of the bright and dark displays is very effective.

Moreover, the first color filter is provided between the first substrateand the second substrate and the second color filter is provided on therear face of the reflection-type polarizing film or the cholestericliquid crystal polymer film, whereby in the case of the reflectiondisplay, light passes through the first color filter twice to displaycolor information, and in the dark display the second color filter isemployed as an absorbing layer by the absorption characteristic thereof.Meanwhile, in the case of the transmission display while the auxiliarylight source is turned on, since light passes through the second colorfilter and the first color filter to display color information, thefirst color filter can be optimized for the reflection display andchroma of the transmission display can be improved by the second colorfilter compared with the case where only the first color filter isprovided, thereby enabling improvement of both the displays of thereflection display and the transmission display.

It should be noted that since the reflection display requires a brightdisplay, a gradation signal is so set that the halftone thereof isdeviated in the bright direction. Thereby, a bright display becomespossible. However, in the case of the transmission display, contrast andchroma are important. Especially, when the external light source is verydark, since an observer becomes very sensitive to brightness, thegradation signal is so set that the halftone thereof is deviated toblack side compared with the reflection display, thereby preventing alarge change in display by ON and OFF of lighting of the auxiliary lightsource. In other words, correction of the gradation signal is changed inaccordance with ON and OFF of lighting of the auxiliary light source,thereby making the display quality excellent.

Furthermore, correction of the gradation signal by which halftone isdeviated in a bright direction or in a dark direction can be changeddepending on the brightness of the environment where the liquid crystaldisplay device is used by the external light source, thereby enablingimprovement of the display quality also in the case where the reflectiondisplay is performed.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 and FIG. 2 are partly enlarged sectional views, corresponding toa section along the A—A line in FIG. 16, of a liquid crystal displaypanel of a liquid crystal display device of a first embodiment of thepresent invention. FIG. 1 is a view for explaining a display functionwhen an external light source is used, and FIG. 2 is a view forexplaining a display function when an auxiliary light source is used;

FIG. 3 is a block diagram of a drive circuit provided in the liquidcrystal display device of the first embodiment of the present invention;

FIG. 4 is an explanatory view for comparing bright and dark displaysbetween the present invention and the conventional example;

FIG. 5 is a diagram showing relations between applied voltage andtransmittance of a liquid crystal showing a gradation display in adisplay;

FIG. 6 and FIG. 7 are sectional views similar to FIG. 1 and FIG. 2 ofthe liquid crystal display panel of the liquid crystal display device ofa second embodiment of the present invention;

FIG. 8 is a sectional view similar to FIG. 1 showing the liquid crystaldisplay panel of the liquid crystal display device of a third embodimentof the present invention;

FIG. 9 is a schematic plane view of a wristwatch in which the liquidcrystal display device shown in FIG. 8 is installed, and FIG. 10 is asectional view along the B—B line in FIG. 9;

FIG. 11 and FIG. 12 are sectional views similar to FIG. 1 and FIG. 2 ofthe liquid crystal display panel of the liquid crystal display device ofa fourth embodiment of the present invention;

FIG. 13 is a block diagram of the drive circuit provided in the liquidcrystal display device of the fourth embodiment of the presentinvention;

FIG. 14 is a diagram showing relations between applied voltage andtransmittance of a liquid crystal showing a gradation display in adisplay where the environment is dark and where the liquid crystaldisplay device of the embodiment of the present invention is used;

FIG. 15 is a diagram showing relations between applied voltage andtransmittance of the liquid crystal showing a gradation display in adisplay where the environment is slightly bright where the liquidcrystal display device of the same is used;

FIG. 16 is a plane view showing an example of the structure of aconventional liquid crystal display device; and

FIG. 17 is a partly enlarged schematic sectional view along the A—A linein FIG. 16.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the best mode of a liquid crystal display device forcarrying out the present invention will be described with reference tothe drawings.

First Embodiment

A first embodiment of the liquid crystal display device according to thepresent invention will be explained with reference to FIG. 1 to FIG. 5and FIG. 16.

FIG. 1 and FIG. 2 are partly enlarged sectional views of a liquidcrystal display panel of the liquid crystal display device showing thefirst embodiment of the present invention and correspond to an enlargedsectional view along the A—A line that in FIG. 16. The plane viewshowing the basic structure of the liquid crystal display device is thesame as in FIG. 16, and thus the illustration thereof is omitted.Incidentally, FIG. 1 is a view for explaining display operations in thecase where a display is performed by utilizing an external light sourceas a main light source, and FIG. 2 is a view for explaining displayoperations in the case where a display is performed by utilizing anauxiliary light source.

The liquid crystal display panel of the liquid crystal display deviceshowing the first embodiment of the present invention shown in FIG. 1and FIG. 2 has the same structure as the liquid crystal display panelthat is explained in FIG. 16 and FIG. 17 except that a light absorbinglayer provided on the rear face of a first polarizing film 11 isdifferent and an auxiliary light source is provided, but it is explainedto make sure.

In this liquid crystal display device, a first substrate 1 and a secondsubstrate 5 made of a transparent material such as glass or the like areoppositely disposed to each other, a predetermined gap between them iskept by a spacer not shown, peripheries of them are bonded together by asealant 4 serving as an adhesive, and a liquid crystal layer 8 is filledin the gap and sealed by an end-sealing material 26 (Refer to FIG. 16).

Moreover, M pieces of scanning electrodes (signal electrodes) 2 made ofa transparent electrode film are formed on the inner face of the firstsubstrate 1, and N pieces of data electrodes (opposed electrodes) 6intersecting the scanning electrodes 2 are formed on the inner face ofthe second substrate 5, and intersections of the scanning electrodes 2and the data electrodes 6 form pixel portions (shown by 21 in FIG. 16)to form a matrix-type liquid crystal display panel having an M×N pieceof pixel portions.

The above liquid crystal display panel may be a liquid crystal displaypanel of an active-matrix type having a switching element in each pixelportion or a liquid crystal display panel of a passive-matrix typewithout providing a switching element, and the liquid crystal displaypanel as the passive-matrix type is explained here.

An alignment layer 3 and an alignment layer 7 are formed on the innerface of the first substrate 1 and the scanning electrodes 2 and on theinner face of the second substrate 5 and the data electrodes 6respectively in order to align the liquid crystal molecules of theliquid crystal 8 regularly.

Moreover, a first polarizing film 11 (hereinafter referred to as areflection-type polarizing film 11) which is a reflection-typepolarizing film is disposed on the rear face side of the first substrate1, which is the side opposite to the observer's side (the visible side:the upper side in FIGS. 1 and 2) of the liquid crystal cell, and asecond polarizing film 12 (hereinafter referred to as a absorption-typepolarizing film 12) which is an absorption-type polarizing film isdisposed on the front face side of the second substrate which is theobserver's side.

The reflection-type polarizing film 11 and the absorption-typepolarizing film 12 are arranged in such a manner that respectivetransmission axes are orthogonal to each other. For the liquid crystallayer 8, twisted nematic liquid crystal is used, for optically rotatingpassing light about 90 degrees between the first substrate 1 and thesecond substrate 5.

Moreover, a printed layer 14 which has many opening portions 14 a with alarge transmittance and which is a light absorbing layer made byprinting with black ink except for the opening portions 14 a with hightransmittance is provided on the rear face of the reflection-typepolarizing film 11. The opening portions 14 a are formed byoffset-printing dot shapes with ink having resinous pigment or bysucker-rubber printing, screen-printing in mesh, applying with a spray,or by forming them through a photolithography using a photoresist resinwhen the printed layer 14 is formed on the reflection-polarizing film11.

An auxiliary light source 9 is disposed on the rear face side of theprinted layer 14 with a slightly spaced gap therebetween. It ispreferable to use a planer light-emitting element which emits light withuniform intensity over the entire liquid crystal display panel, forexample, an electro-luminescent (EL) light as the auxiliary light source9.

Display operations of the liquid crystal display panel will now beexplained.

When the environment is bright where the liquid crystal display panel isused, external light used as the main light source is incident from thefront face of the second substrate on the visible side to the liquidcrystal display panel as shown in FIG. 1. Therefore, at a pixel portionfor performing a dark display, a first incident ray of light L1 passesthrough the absorption-type polarizing film 12 to become a linearlypolarized light, is optically rotated 90° by the liquid crystal layer 8and is incident to the reflection-type polarizing film 11 as a lightlinearly polarized in the direction parallel to the transmission axisthereof, so that the light passes through the reflection-type polarizingfilm 11 and is absorbed by the printed layer 14 at a portion where theopening portion 14 a is not provided.

Further, an incident light L4 which passes through the opening portion14 a in the printed layer 14 disposed on the rear face of thereflection-type polarizing film 11 passes through the opening portion 14a and thereafter part of the light is reflected by the auxiliary lightsource 9 disposed on the rear face side of the printed layer 14 to beemitted to the printed layer 14 side again, but it is absorbed by theprinted layer 14 and hence it does not reach the visible side. Asdescribed above, leaking light in a dark display of the incident lightL4 passing through the opening portion 14 a which has not been absorbedby the printed layer 14 is also absorbed by the printed layer 14 aroundthe opening portion 14 a, whereby the dark display does not deteriorate.

Moreover, as for a bright display, a second incident light L2 passesthrough the absorption-type polarizing film 12 to become a linearlypolarized light and passes through, without being optically rotated, aportion of the liquid crystal layer 8 where optical activity thereof islost by a large voltage being applied to the liquid crystal layer 8, andis incident to the reflection-type polarizing film 11 as a lightlinearly polarized in the direction parallel to the reflection axisthereof, whereby the light is reflected by the reflection-typepolarizing film 11 to become a strong reflected light L3 and passesthrough the liquid crystal layer 8 and the absorption-type polarizingfilm 12 to go out to the visible side (the upper side in FIG. 1).

As above, for the bright and dark displays utilizing the external lightsource, it becomes possible that the dark display is performed by thelinearly polarized light being incident to the transmission axis of thereflection-type polarized film 11 and the absorption characteristic ofthe printed layer 14 and the bright display is performed by thereflection characteristic of the reflection-type polarizing film 11.

Meanwhile, when the environment is dark where the liquid crystal displaypanel is used, the auxiliary light source 9 is turned on, whereby lightsL21, L22 and L23 are emitted from the auxiliary light source 9 to thefirst substrate 1 side as shown in FIG. 2. Though part of the emittedlight from the auxiliary light source 9 is absorbed by the printed layer14, the light passing through the opening portion 14 a passes throughthe first substrate 1, the liquid crystal layer 8, the second substrate5 and the absorption-type polarizing film 12 to go out to the visibleside (the upper side in FIG. 2), resulting in the bright display.

The outgoing light from the absorption-type polarizing film 12 isdiffused and goes out as shown by the light L21 by providing a frontdiffusing layer (not shown) containing plastic beads in a photoresist onthe front face of the absorption-type polarizing film 12, therebyenabling an excellent display without depending on a viewing angle.

At the portion of the liquid crystal layer 8 where the optical rotatorythereof is lost by a voltage being applied to the liquid crystal layer8, the light which is emitted from the auxiliary light source 9 andpasses through the opening portion 14 a of the printed layer 14 passesthrough the reflection-type polarizing film 11 to become a linearlypolarized light and passes through the liquid crystal layer 8 withoutbeing optically rotated to be incident to the absorption-type polarizingfilm 12 as a light linearly polarized in the direction parallel to theabsorption axis thereof, so that the light is absorbed by theabsorption-type polarizing film 12 and hence it does not go out to thevisible side, resulting in a dark display.

To solve reversal of brightness and darkness of a display between thereflection display by the extraneous light and in the transmissiondisplay by the auxiliary light source as above, a gradation signal whichis applied to the data electrodes 6 is reversed by a drive circuit fordriving the liquid crystal display panel synchronously with turning onthe auxiliary light source 9. Thereby, when the transmission display isperformed by the auxiliary light source 9, a gradation of bright anddark displays are reversed in relation to the reflection displayutilizing the external light, thereby preventing brightness and darknessof a display from being reversed between the reflection display usingthe external light and the transmission display using the auxiliarylight source 9.

Thus, a block diagram of the drive circuit of the liquid crystal displaydevice used for this embodiment is shown in FIG. 3 and will now beexplained.

In the drive circuit of the liquid crystal display device, an electricsource voltage suitable for each block is generated in a power sourcecircuit 31 for causing each circuit block to operate and supplied toeach circuit block 32. A basic clock signal is produced by a basic clockoscillation circuit 33 which is a time operation standard of a circuitand applied to a vertical synchronization circuit 40 and a horizontalsynchronization circuit 38 through a synchronization separation circuit35 in response to an input of an image signal 34. Moreover, to generatea gradation (bright and dark) signal which is applied to the liquidcrystal layer 8 in response to the image signal 34, a signal that is theimage signal A/D-converted by an A/D converter 36 is input to agradation reversal circuit 37 for reversing a gradation signal dependingon use of the external light or use of the auxiliary light source 9.

Moreover, an output signal of the gradation reversal circuit 37 is inputto a data electrode drive circuit 42 as a gradation signal through agradation signal generating circuit 41 to apply a gradation signal of avoltage waveform for performing bright and dark displays on the dataelectrodes on the second substrate 5 of a liquid crystal display panel10.

Furthermore, an output signal of the horizontal synchronization circuit38 is input to a scanning electrode drive circuit 43 to apply apredetermined voltage waveform from the scanning electrode drive circuit43 to select a plurality of scanning electrodes on the first substrate 1of the liquid crystal display panel 10 in a time sequence.

Due to the above drive circuit, the gradation reversal circuit 37 isswitched by a setting of ON and OFF of the auxiliary light source switch39 to control reversal/non-reversal of a gradation signal, therebyperforming the reflection display through the use of the external lightsource and the transmission display by turning on the auxiliary lightsource 9 on the liquid crystal display panel 10 without producing thereversal of brightness and darkness.

The liquid crystal display device for a monochrome display in which acolor filter is not provided is explained in the first embodiment.However, even when a color filter is provided, the printed layer 14having the opening portions 14 a and the gradation reversal circuit 37are provided in the case where the external light source is utilized andin the case where the auxiliary light source 9 is used as in the firstembodiment and the gradations are reversed between each other in thecase where the external light source is utilized and in the case wherethe auxiliary light source 9 is used, thereby making it possible that amust-be bright display is the bright display and a must-be dark displayis the dark display in both displays.

Next, reverse displays of the bright and dark displays of the liquidcrystal display device will be described. FIG. 4 is a view showingstates of displays of the reflection-type display using the externallight and the transmission-type display using the auxiliary light sourcein a conventional example (Y) and in an embodiment (X) of the presentinvention of liquid crystal display devices. The reversal of the brightand dark displays of the liquid crystal display device will be explainedwith FIG. 4.

First, when the external light source is utilized, in displays in theliquid crystal display devices of this embodiment (X) and theconventional example (Y), squares 60, triangles 61 and circles 62 aredisplayed in order of brightness on display screens 59 with the maximumbrightness. More specifically, when the external light source isutilized, displays of this embodiment (X) and the convention example (Y)are the same. In this case, each of them uses the reflectioncharacteristic of the reflection-type polarizing film within a regionwhere the brightness is high and uses the transmission characteristic ofthe reflection-type polarizing film and the absorption characteristic ofthe printed layer provided on the rear face of the reflection-typepolarizing film within a region where the brightness is low.

Next, a case where the external environment becomes dark and thusturning on the auxiliary light source 9 is required is explained. Theauxiliary light source is automatically turned on by detecting light inthe external environment by means of a photosensor or has a function forautomatically turning on depending on a positional relation between anobserver and the liquid crystal display device by means of an anglesensor. Alternatively, the observer can turn on the auxiliary lightsource 9 through an operation of turning the auxiliary light sourceswitch 39 in FIG. 3 ON as required.

By turning on the auxiliary light source, since the printed layer isprovided on the entire surface of the rear face of the reflection-typepolarizing film in the conventional example (Y), the light from theauxiliary light source is absorbed largely. However, the printed layeris given a transmission characteristic, whereby in the case where thelight of the auxiliary light source passes through the reflection-typepolarizing film, the liquid crystal layer and the second polarizing filmto go out to the observer's side, the light of the auxiliary lightsource strongly goes out to the observer's side within a region wherethe transmittance thereof is large (a dark display region) when theexternal light is utilized, resulting in a bright display. The light ofthe auxiliary light source is shut within a region where the reflectioncharacteristic is strong (a bright display region) when the externallight source in utilized, resulting in a dark display.

As shown in FIG. 4, a circle 66, a triangle 65 and a square 64 aredisplayed in order of brightness in a dark display screen 63 by turningon the auxiliary light source in the conventional example (Y). In otherwords, the brightness order of the square 60, the triangle 61 and thecircle 62 when the external light source is utilized is changed into areverse brightness order (reversal of brightness and darkness) of thecircle 66, the triangle 65 and the square 64 when the auxiliary lightsource is used.

As compared with the above, in this embodiment, the printed layerdisposed on the rear face of the reflection-type polarizing film isprovided with opening portions with a large transmittance, so that theamount of light going out to the observer's side can be increased byturning on the auxiliary light source. Moreover, the gradation reversalcircuit 37 is provided to reverse a gradation signal while the auxiliarylight source is turned on. Therefore, a small voltage is applied topixel portions while the auxiliary light source is turned on which applya large voltage to the liquid crystal layer while the external lightsource is utilized, and conversely a large voltage is applied to pixelportions while the auxiliary light source is turned on which apply asmall voltage to the liquid crystal layer while the external lightsource is utilized.

Next, operations of the gradation reversal circuit 37 of this embodimentis explained using FIG. 5 which is a diagram showing a relation betweenthe voltage applied to the liquid crystal layer and the transmittance.

The characteristics of the applied voltage and the transmittance whenthe external light source is utilized are shown by a solid line L andthe characteristics when the auxiliary light source is used are shown bya broken line M. It is preferable to show brightness by the reflectancewhen the external light source is utilized, but it is shown by thetransmittance for convenience. The difference in brightness of a displayby the liquid crystal display panel is displayed by the gradation andcontrolled by the voltage applied to the liquid crystal layer.

As shown in FIG. 5, the voltage applied to the liquid crystal layer inthe case of a large transmittance T1 is an applied voltage V1 on thecurved line L and an applied voltage V0 on the curved line M, and V1 islarger than V0. Conversely, the voltage applied to the liquid crystallayer in the case of a small transmittance T2 is an applied voltage V3on the curved line L and an applied voltage V2 on the curved line M, andV2 is larger than V3.

As described above, the voltages showing the equivalent transmittanceare reversed between the characteristics shown by the curved line L andthe characteristics shown by the curved line M. Therefore, the gradationreversal circuit is a circuit for correcting the voltage applied to theliquid crystal so as to make the transmittances equivalent for the casewhen the external light source is utilized and for the case when theauxiliary light source is used.

Moreover, the applied voltages are reversed between the case where theexternal light source is used and the case where the auxiliary lightsource is used and additionally different relations between thegradation and the applied voltage are utilized so that the gradation isconcentrated in a direction to increase the transmittance when theexternal light source in utilized and the applied voltage is divided tobe averaged entirely when the auxiliary light source is used, therebyperforming a bright display in the case where the external light sourceis utilized for which brightness is especially required.

As described above, in the conventional liquid crystal display device,the reversal of the bright and dark displays occurs between the displayusing the external light source and the display using the auxiliarylight source. However, in the liquid crystal display device of thisembodiment, the reversal of the bright and dark displays does not occurby virtue of the operation of the gradation reversal circuit. Moreover,the printed layer provided on the rear face of the reflection-typepolarizing film has the opening portions, thereby enabling a brightdisplay when the auxiliary light source is used.

Furthermore, as shown in FIG. 1, in the case where the light from theexternal light source passes through the absorption-type polarizing film12, the liquid crystal layer 8 and the reflection-type polarizing film11, and further passing through the opening portion 14 a provided in theprinted layer 14 to reach the auxiliary light source 9, it is preferablethat an electro-luminescent (EL) light is used for the auxiliary lightsource 9 and the surface of the EL light is subjected to low-reflectionprocessing to be made a surface with low reflection strength.Alternatively, the surface of the EL light is given scatteringproperties and a relation between the observer and the incident lightand a relation between the area of the opening portion 14 a and the areaof the printed layer 14 around the opening portion 14 a are used,thereby decreasing the reflected light from the front face of theauxiliary light source 9.

Second Embodiment

The second embodiment of the liquid crystal display device according tothe present invention is explained with reference to FIG. 6 and FIG. 7.

FIG. 6 and FIG. 7 are partly enlarged sectional views of the liquidcrystal display device showing the second embodiment of the presentinvention and correspond to an enlarged sectional view along the A—Aline in FIG. 16. The plane view showing the basic structure of theliquid crystal display device is also the same as FIG. 16, and thus theillustration thereof is omitted. FIG. 6 is a view for explaining displayoperations in the case where a display is performed using an externallight source as a main light source, and FIG. 7 is a view for explainingdisplay operations in the case where a display is performed using anauxiliary light source.

The points of the liquid crystal display panel of this embodiment differfrom those in the liquid crystal display panel of the aforesaid firstembodiment, in that a scattering film 16 is disposed on the rear face ofa reflection-type polarizing film 11 as the first polarizing film, and aprinted layer 14 having opening portions 14 a is provided on anauxiliary light source 9 on the rear face side of the scattering film 16with a predetermined gap therebetween. This is for the sake ofreinforcing the strength of the printed layer 14.

For the auxiliary light source 9, an EL light may be used as in thefirst embodiment, but a light source composed of a cold-cathode tube anda light guide film is used in this embodiment.

On the rear face of the printed layer 14, a light emitting element isnot directly provided and the light guide film is disposed, and a mainlight source portion of the auxiliary light source 9 is provided aroundthe liquid crystal display panel, whereby reflection from the front faceof the auxiliary light source 9 can be prevented when the external lightsource is utilized.

Moreover, the printed layer 14 in this embodiment employs a structurehaving an opaque portion in grating form (in grid form) and the openingportions 14 a. More specifically, the printed layer 14 is made of athick photoresist mixed with a black pigment having a thickness of 10 μmand the width of a printed portion thereof is made 15 μm and the widthof the opening portion 14 a is made 3 μm by a photolithography method.When moiré occurs due to width of the scanning electrode and the widthof the data electrode at the pixel portion, the width of the printedportion of the printed layer 14 and the width of the opening portion 14a thereof are changed.

The other structure of the liquid crystal display panel of the secondembodiment is the same as that of the first embodiment, and thus thedescription thereof is omitted.

The liquid crystal display panel of this embodiment uses the opaqueportions (printed portions) in grating form and the opening portions 14a of the printed layer 14, whereby when the incident angle of the lightfrom the external light source tilts 30 degrees or more in relation to aperpendicular line of the absorption-type polarizing film 12, the lightis absorbed due to the thickness of the printed layer 14 and hence itdoes not reach the front face of the auxiliary light source 9.Therefore, an excellent contrast ratio can be obtained when the externallight source is utilized by suitable positioning of the main lightsource of the auxiliary light source 9 and employment of the printedlayer 14 in grating form having the opening portions 14 a.

Relations between the reflection axis of the reflection-type polarizingfilm 11, the transmission axis of an absorption-type polarizing film 12and the liquid crystal layer 8 are the same as in the first embodiment.

Therefore, when the environment is bright where the liquid crystaldisplay panel is used, as shown in FIG. 6, a first incident ray of lightL1 at a dark display portion passes through the reflection-typepolarizing film 11 through the same path as in the case of the firstembodiment and becomes a scattered light by the scattering film 16having light scattering properties to be absorbed by the printed layer14.

The gap is provided between the scattering film 16 and the printed layer14, whereby the scattered light is absorbed efficiently by the printedlayer 14 in grating form.

A second incident light L2 at a bright display portion is reflected bythe reflection-type polarizing film 11 as in the first embodiment andbecomes a strongly reflected light L3 to go out to the visible side.

As described above, in the bright and dark displays when the externallight source is used, the dark display is performed by the linearlypolarized light being incident to the transmission axis of thereflection-type polarizing film 11 and the absorption characteristic ofthe printed layer 14, and the bright display is performed by thereflection characteristic of the reflection-type polarizing film 11.

Next, when the environment is dark where the liquid crystal displaypanel is used, as shown in FIG. 7, the auxiliary light source 9 isturned on, whereby a light L21, which the auxiliary light source 9 emitsgoes out to the first substrate 1 side. In this case, the light from theauxiliary light source 9 decreases in divergence angle, and the lightpassing through the opening portion 14 a of the printed layer 14 isscarcely absorbed at a midpoint by the printed layer 14 in grating formand scattered as scattered lights L24 and L25 by the scattering film 16disposed on the rear face of the reflection-type polarizing film 11, andfurther passes through the liquid crystal layer 8 and theabsorption-type polarizing film 12 to go out to the visible side,thereby enabling a bright display.

As for the scattering film 16, a plastic plate made by formingasperities on the surface of plastic, or by mixing beads with differentrefractive indexes in plastic is bonded to the rear face of thereflection-type polarizing film 11 with an adhesive.

However, only with the above structure, the bright and dark displays arereversed in the case of the display using the auxiliary light source 9in relation to the case of the reflection display using the externallight source, by the characteristics of the reflection-type polarizingfilm 11, the liquid crystal layer 8 and the absorption-type polarizingfilm 12 as described in the description of the first embodiment.

Therefore, a drive circuit having a gradation reversal circuit 37 asshown in FIG. 3 is provided to drive the liquid crystal display panel asin the case of the first embodiment, the gradation reversal circuit isoperated when the auxiliary light source is turned on to reverse agradation signal applied to data electrodes of a liquid crystal displaypanel 10, thereby preventing the bright and dark displays from beingreversed between the case where the external light source is used andthe case where the auxiliary light source 9 is used.

Third Embodiment

The third embodiment of the present invention is explained withreference to FIG. 8 to FIG. 10.

FIG. 8 is a partly enlarged sectional view of a liquid crystal displaypanel of the liquid crystal display device of the third embodiment ofthe present invention and corresponds to an enlarged sectional viewalong the A—A line in FIG. 16. The plane view showing the basicstructure of the liquid crystal display device is also the same as thatin FIG. 16 and thus the illustration thereof is omitted.

FIG. 9 is a schematic plane view of a wristwatch in which the liquidcrystal display device of the third embodiment is installed, and FIG. 10is a sectional view along the B—B line in FIG. 9.

The liquid crystal display panel of the third embodiment is explainedonly about the points differing from the liquid crystal display panel ofthe first embodiment.

A super twisted nematic (STN) liquid crystal layer 8 is used as a liquidcrystal layer 8 filled in a gap between a first substrate 1 and a secondsubstrate 5. Moreover, alignment films 3 and 7 are provided on the firstsubstrate 1 and the second substrate 5 to align liquid crystal moleculesof the STN liquid crystal layer regularly, and further the alignmentfilms 3 and 7 are subjected to rubbing processing. Furthermore, a chiralmaterial is added to twist the liquid crystal.

As shown in FIG. 8, a retardation film 74 is provided on the secondsubstrate 5 to prevent the STN liquid crystal layer 8 from beingcolored, and an absorption-type polarizing film 12 is disposed thereon(on the visible side). Moreover, a quarter-wavelength film (not shown)for adjusting polarization characteristics of the STN liquid crystallayer 8 and a cholesteric liquid crystal polymer film 73 capable ofselectively reflecting light within a visible light region are providedon the rear face side of the first substrate 1.

The cholesteric liquid crystal polymer film 73 has a reflectioncharacteristic in a strong metallic tone selectively to light incidentfrom the second substrate 5 side and is capable of efficientlytransmitting light with a wavelength except for the selectivelyreflecting region. Therefore, a difference is given to chromaticity (x,y values) of a printed layer 14′ provided on the rear face side of thecholesteric liquid crystal polymer film 73 from chromaticity of theselectively reflecting region of the cholesteric liquid crystal polymerfilm 73, or brightness (an L value) of the printed layer 14′ is madelower than brightness of the cholesteric liquid crystal polymer film 73,thereby enabling a display excellent in visibility.

The selectively reflecting wavelength region of light of the cholestericliquid crystal polymer film 73 changes depending on a positionalrelation between a direction in which light is incident to thecholesteric liquid crystal polymer film 73 and an observer. This isbecause a relative thickness of the cholesteric liquid crystal polymerfilm 73 changes depending on an incident angle of light.

For instance, in the case where the cholesteric liquid crystal polymerfilm 73 for selectively reflecting a yellow wavelength is used, sinceyellow changes to green depending on the direction of the observer, aprinted layer 14′ with a wavelength region different from yellow andgreen or with low brightness including a yellow wavelength is used forthe printed layer 14′.

In this third embodiment, opening portions are not particularly formedin the printed layer 14′, and a printed layer having transparency isemployed so that the printed layer 14′ transmits part of light withinthe visible light region. In other words, the entire surface of theprinted layer 14′ is made to transmit part of light.

Through the use of the cholesteric liquid crystal polymer film 73, theliquid crystal display panel of this embodiment can use the mirror-likeselectively reflection characteristic of the visible wavelength regionand has a transmission characteristic except for the selectivelyreflecting wavelength region, so that a display with an excellentcontrast ratio becomes possible by giving a difference between thechromaticity (x, y) of the printed layer 14′ provided on the case backside of the first substrate 1 and the chromaticity (x, y) of theselectively reflecting region.

The brightness (L) of the printed layer 14′ is decreased, whereby theselectively reflection characteristic of the cholesteric liquid crystalpolymer film 73 has a characteristic of a metallic tone, so that itbecomes possible to use the reflection characteristic of the cholestericliquid crystal polymer film 73 efficiently by decreasing the reflectioncharacteristic of the printed layer 14′.

In the case where a display is performed by this liquid crystal displaypanel using the external light source, the display is performed by theselectively reflection characteristic and the transmissioncharacteristic of the cholesteric liquid crystal polymer film 73.Therefore, the bright display is performed by the selective reflectionby means of the cholesteric liquid crystal polymer film 73 and the darkdisplay is performed by the absorption characteristic of the printedlayer 14′ disposed on the rear face of the cholesteric liquid crystalpolymer film 73 owing to the transmission characteristic or by thedifference in chromaticity.

However, in the case where the display is performed using the differencein chromaticity, when the reversal of the bright and dark displays byturning on the auxiliary light source 9 is prevented, light absorptionoccurs because of a difference between an emitting light wavelength ofthe auxiliary light source 9 and a transmitting wavelength of theprinted layer 14′, resulting in a decrease in brightness. Therefore,means for preventing the reflection characteristic of the printed layer14′ is employed. More specifically, a resin containing carbon is usedand the amount of carbon contained in the resin is controlled to have anaverage absorption characteristic within the visible light region,thereby controlling the whole transmittance.

The emitting light wavelength of the auxiliary light source 9 providedon the rear face side of the printed layer 14′ is matched with theselecting wavelength of the cholesteric liquid crystal polymer film 73so that the light which is almost the same as the selectively reflectioncharacteristic of the cholesteric liquid crystal polymer film 73 goesout to the observer at the transmitting portion of the cholestericliquid crystal polymer film 73 by turning on the auxiliary light source9. Conversely, the light within the selecting wavelength region comesinto a dark display because the light emitted by turning on theauxiliary light source 9 is shut off, resulting in a display reversedfrom that in the case where the external light source is utilized.

Therefore, a gradation reversal circuit is used as in the liquid crystaldisplay device in each of the aforesaid embodiments and further theemitting light wavelength of the auxiliary light source 9 is made almostthe same as the reflection characteristic of the cholesteric liquidcrystal polymer film 73, thereby preventing the reversal of the displayby the external light source and the auxiliary light source 9.

As is clear from the above description, this liquid crystal displaydevice uses a display mode for reflecting part of the wavelength regionof the visible light and for transmitting or absorbing the light withinthe other wavelength region.

For instance, in the case where the liquid crystal display device usingthe cholesteric liquid crystal polymer film 73 as in this embodiment,when the external light source is used, a display is performed by brightcolors within the selectively reflecting region and absorption by theprinted layer 14′ provided on the rear face of the cholesteric liquidcrystal polymer film 73 or by the difference in chromaticity.

In this case, the selectively reflecting pixel portions displaying abright color come into a dark display by turning on the auxiliary lightsource 9 because the transmittance thereof is low compared with that ofa pixel portions in a reverse dark color, resulting in a reversal of thebright and dark displays.

Therefore, as shown in the third embodiment, the emitting lightwavelength of the auxiliary light source 9 is selected, the printedlayer 14′ has a light transmitting characteristic, and the gradationreversal circuit operating synchronously with turning on the auxiliarylight source 9 is employed, thereby achieving a display with excellentvisibility for the observer without occurrence of a reversal of brightand dark displays in the reflection display using the external lightsource and in the transmission display using the auxiliary light source9.

An embodiment in which the liquid crystal display device of the thirdembodiment is installed in a wristwatch is shown in FIG. 9 and FIG. 10.

In this wristwatch, in an airtight package composed of a watch case, aglass 81, and a case back 82 (mainly as shown in FIG. 9), a dial cover79, the absorption-type polarizing film 12 as the second polarizingfilm, the retardation film 74, the second substrate 5, the liquidcrystal layer 8, the first substrate 1, the cholesteric liquid crystalpolymer film 73, the printed layer 14′ having a light transmittingcharacteristic, and the auxiliary light source 9 are provided from theglass 81 side.

The liquid crystal layer 8 is sealed between the first substrate 1 andthe second substrate 5 with a sealant 4 and an end-sealing material (notshown).

On the case back 82 side under the first substrate 1, a circuit board 83having a drive circuit for driving the liquid crystal display panel asshown in FIG. 3 and a battery 84 are provided. The electrical connectionbetween the circuit board 83 and the liquid crystal display panel isperformed by means of a zebra-rubber 85 in which conductive portions andnonconductive portions in stripes are laminated repeatedly.

A fixing metal support 86 is provided to reinforce the connectionbetween the liquid crystal display panel and the circuit board 83 and tomatch the liquid crystal display panel with the watch case 75.

As shown in FIG. 9, an a.m. and p.m. display 76, and an hour display 77and a minute display 78 by numbers can be performed by the liquidcrystal display panel. Moreover, a setting terminal input portion 80 forperforming time adjustment and turning on the auxiliary light source 9is provided on the side face of the watch case 75.

On the glass 81 side of the second substrate 5, the dial cover 79 isprovided so that a connecting portion between the second substrate 5 andthe circuit board 83 and the sealant 4 can not be seen by the observer.

In the liquid crystal display device structured as above and thewristwatch using the liquid crystal display device, electric signals areapplied to the scanning electrodes 2 on the first substrate 1 and thedata electrodes 6 on the second substrate 5 and a voltage is applied tothe liquid crystal layer 8, thereby controlling an opticalcharacteristic of the STN liquid crystal layer 8, and a display byselective reflection can be realized by means of the cholesteric liquidcrystal polymer film 73, the absorption-type polarizing film 12 and theretardation film 74.

As described above, the liquid crystal display device according to thepresent invention is used in a timepiece, whereby the reflectioncharacteristic in a metallic tone of the cholesteric liquid crystalpolymer film 73 can be utilized, so that improvement of attractiveappearance and a bright time display can be realized.

Fourth Embodiment

The fourth embodiment of the present invention is explained withreference to FIG. 11 to FIG. 15.

FIG. 11 and FIG. 12 are partly enlarged sectional views of the liquidcrystal display device showing the fourth embodiment of the presentinvention and correspond to an enlarged sectional view along the A—Aline in FIG. 16. The plane view showing the basic structure of theliquid crystal display device is also the same as that in FIG. 16, andthus the illustration thereof is omitted. FIG. 11 is a view forexplaining display operations in the case where a display is performedutilizing an external light source as a main light source, and FIG. 12is a view for explaining display operations in the case where a displayis performed using an auxiliary light source.

The points of the liquid crystal display panel of the fourth embodimentthat differ from the liquid crystal display panel of the firstembodiment are that a first color filter 90 is provided on a firstsubstrate 1, a scattering film 16 is disposed on the front face of afirst polarizing film 11, and a second color filter 94 is provided onthe rear face of the reflection-type polarizing film 11 which is thefirst polarizing film as a printed layer.

The remaining structure is the same as that of the first embodimentshown in FIG. 1 and FIG. 2, and thus the description thereof is omitted.

The first color filter 90 composed of red color filters 91, green colorfilters 92 and blue color filters 93 is provided on the inner face ofthe transparent first substrate 1 of this liquid crystal display panel,and a protection insulating film (not shown) is provided on the firstcolor filter 90, and M pieces of scanning electrodes 2 made of atransparent electrode film are formed on the protection insulating film.

Moreover, the scattering film 16 having light scattering properties isprovided on the front face side of the reflection-type polarizing film11 which is the first polarizing film, and the second color filter 94composed of red color filters 95, green color filters 96 and blue colorfilters 97 which are the same sizes and the same colors as respectivered, green and blue color filters 91, 92 and 93 of the first colorfilter 90, is provided on the rear face side thereof. The second colorfilter 94 functions as a light absorbing layer during the reflectiondisplay by the external light.

An auxiliary light source 9 is provided on the under face side of thesecond color filter 94 with a predetermined gap therebetween. Theauxiliary light source 9 is composed of a cold-cathode tube and a lightguide film.

The reflection-type polarizing film 11 and the absorption-typepolarizing film 12 are arranged in directions so that the transmissionaxes thereof are orthogonal to each other, and a twisted nematic (TN)liquid crystal layer for optically rotating passing light about 90°between the first substrate 1 and the second substrate 5 is used as theliquid crystal layer 8.

Therefore, when the environment is bright where the liquid crystaldisplay device is used, as shown in FIG. 11, the external light isincident from the visible side of this liquid crystal display panel.Thus, at pixel portions for performing a dark display, a first incidentlight L1 passes through the second polarizing film 12 to become alinearly polarized light and is optically rotated 90° by the liquidcrystal layer 8, it then passes through the first color filter 90 tobecome a scattered light by the scattering film 16, and is incident tothe reflection-type polarizing film 11 as a light linearly polarized inthe direction parallel to the transmission axis thereof, so that thelight passes through the reflection-type polarizing film 11 and isincident to the second color filter 94 serving as an absorbing layer.Since reflection from the second color filter 94 is very low, outgoinglight by the reflection becomes weak light, resulting in a dark display.

Moreover, at pixel portions for performing a bright display, a secondincident light L2 passes through the second polarizing film 12 to becomea linearly polarized light, optical rotatory of the liquid crystal layer8 is lost by a large voltage being applied to the liquid crystal layer8, and the incident linearly polarized light passes through withoutbeing optically rotated and is incident to the reflection-typepolarizing film 11 as a light linearly polarized in the directionparallel to the reflection axis thereof. Therefore, the incident lightL2 is reflected by the reflection-type polarizing film 11 to become astrong reflected light L3 and is given scattering properties by thescattering film 16 and passes through the liquid crystal layer 8 and theabsorption-type polarizing film 12 to go out to the visible side.

As above, as for the bright and dark displays utilizing the externallight source, the dark display is performed by the linearly polarizedlight being incident to the transmission axis of the reflection-typepolarized film 11 and the absorption characteristic of the second colorfilter 94, and the bright display is performed by the reflectioncharacteristic of the reflection-type polarizing film.

Meanwhile, when the environment is dark where the liquid crystal displaypanel is used, as shown in FIG. 12, the auxiliary light source 9 isturned on, whereby a light L26 goes out to the first substrate 1 side byemission of the auxiliary light source 9. In this case, the light fromthe auxiliary light source 9 passes through the second color filter 94to be changed into colored light by each of the color filters 95, 96 and97, and further passes through the reflection-type polarizing film 11 tobecome a linearly polarized light and is scattered by the scatteringfilm 16 to become scattered lights L27 and 28. Furthermore, passingthrough the first color filter 90, the colored light is emphasized inchroma by each of the color filters 91, 92 and 93 and thereafter passesthrough the liquid crystal layer 8 and the absorption-type polarizingfilm 12 to go out to the visible side, thereby enabling a brightdisplay.

The scattering film 16 can be formed by means for forming asperities onthe surface of plastic, for mixing beads with different refractiveindexes in plastic, or for mixing plastic beads with differentrefractive indexes in an adhesive, or the like.

Through the use of the liquid crystal display device structured asabove, during the reflection display, light is changed to a coloredlight by the first color filter 90, and in the bright display, the lightpasses through the first color filter 90 twice back and forth by thereflection by means of the reflection-type polarizing film 11.

In the dark display, almost all the light passing through thereflection-type polarizing film 11 is absorbed by the absorptioncharacteristic of the second color filter 94.

In contrast to the above, during the transmission display by turning onthe auxiliary light source 9, the emitted light by the auxiliary lightsource 9 is changed to colored light by the second color filter 94, andin the bright display, the light passing through the reflection-typepolarizing film 11 passes through the first color filter 90 to beemitted to the visible side. In the dark display, the light passingthrough the reflection-type polarizing film 11 is modulated by theliquid crystal layer 8 to be absorbed by the absorption-type polarizingfilm 12.

In other words, according to the liquid crystal display device of thefourth embodiment, in the case where only the first color filter 90 isprovided, the light going out to the visible side passes through thefirst color filter twice in the reflection display, but it passesthrough once in the transmission display resulting in a display withpoor chroma. However, as shown in the fourth embodiment, the use of thefirst color filter 90 and the second color filter 94 enables anexcellent display both in the reflection display and in the transmissiondisplay.

However, brightness and darkness of a display are reversed in the casewhere the external light is used and in the case where the auxiliarylight source is used when the same voltage is applied to the liquidcrystal layer 8.

A drive circuit block diagram of the liquid crystal display device usedin this embodiment is shown in FIG. 13. This embodiment is characterizedin that the amount of light in the environment where the liquid crystaldisplay device is used is detected by a light amount sensor 44, turningon the auxiliary light source 9, and reversing gradation by means of agradation reversal and gradation control circuit 29 are simultaneouslyperformed, and deviations of gradations in the reflection display andthe transmission display are controlled. The other portions in the drivecircuit shown in FIG. 13 are the same as those in the drive circuit usedin the first embodiment shown in FIG. 3, and thus the descriptionthereof is omitted.

The gradation reversal and gradation control circuit 29 performs anoperation for reversing gradation signals in response to a detectingsignal of the light amount sensor 44 when the external environmentbecomes dark and the auxiliary light source 9 is turned on. Moreover, inthe case of the reflection display by the external light, the gradationreversal and gradation control circuit 29 controls whether halftonereflection of the display is deviated to the bright side or to the darkside in accordance with the brightness of the external environment. Inthe case of the transmission display by turning on the auxiliary lightsource 9, the gradation reversal and gradation control circuit 29controls whether halftone transmission of the display is deviated to thebright side or to the dark side.

As shown in this drive circuit, ON or OFF of the gradation reversal andgradation control circuit 29 and the auxiliary light source 9 is set bya detecting signal of the light amount sensor 44 andreversal/non-reversal of a gradation signal is controlled, therebydecreasing changes in display quality due to changes in brightness ofthe external environment and turning on or turning off of the auxiliarylight source 9 and simultaneously improving visibility.

Next, gradation controls of the reflection display and the transmissiondisplay, which are performed to improve display quality of the liquidcrystal display device, when the auxiliary light source 9 is turned onand turned off are explained with reference to FIG. 14 and FIG. 15.

In each of the diagrams of FIG. 14 and FIG. 15, the lateral axis showsthe voltage applied to the liquid crystal layer and the vertical axisshows the reflectance and the transmittance. The characteristics of thereflection display using the external light source is shown by a solidline L and the characteristics of the transmission display using theauxiliary light source is shown by a broken line N.

The brightness is shown by the reflectance when the external lightsource is used, and the brightness is shown by the transmittance whenthe auxiliary light source is used. The difference in brightness of theliquid crystal display device is displayed by the gradation, andcontrolled by the voltage applied to the liquid crystal layer. FIG. 14is a diagram showing a control of the gradation reversal and gradationcontrol circuit 29 when the auxiliary light source 9 is turned on andturned off in a dark external environment, and FIG. 15 is a diagramshowing a control of the gradation reversal and gradation controlcircuit 29 when the auxiliary light source 9 is turned on and turned offin a slightly bright external environment.

In FIG. 14 and FIG. 15, the voltage applied to the liquid crystal layer8 in the reflection display and in the transmission display is set, forconvenience, in a direction where the transmittance and the reflectancerise mutually with an increase in voltage.

First, when the external environment is dark, the observer is sensitiveto brightness and is sensitive also to chromaticity of the transmissiondisplay. Therefore, as shown in FIG. 14, at a center voltage Vx of thevoltage applied to the liquid crystal layer, a large reflectance Rx isshown in the reflection display but a small transmittance Tx is shown inthe transmission display.

At a voltage V1 that is a voltage applied to the liquid crystal layer,which is larger than the center voltage Vx, a still large reflectance R1is shown in the reflection display but a very small transmittance T1 isshown in the transmission display. Conversely, at a voltage V2 smallerthan the center voltage Vx, a large reflectance R2, which is almostsaturated, is shown in the reflection display and a considerably smalltransmittance T2 is shown in the transmission display.

In other words, the reflection display is so set that the halftonethereof is deviated in a bright direction where the reflectance islarge, and the transmission display is so set that the halftone thereofis deviated in a dark direction where the transmittance is small. As forthe above setting, since the external environment is dark, a brightsetting is required to secure the visibility when the auxiliary lightsource 9 is turned off. Conversely, since the bright display becomespossible when the auxiliary light source 9 is turned on, thetransmission display is set in the dark direction, thereby making itpossible to decrease the difference between the reflection display andthe transmission display.

Next, when the external environment is comparatively bright, theobserver is not sensitive to brightness and the reflection strength ishigh, resulting in a diagram where the halftone of the reflectiondisplay and the halftone of the transmission display are almost thesame, as shown in FIG. 15.

In other words, the reflection display and the transmission display areset not to have large deviations. Moreover, in a brighter environment,it is enough to use the reflection display only, and it is preferable touse the reflection display so as to extend battery life by reducingpower consumption of the liquid crystal display device.

The gradation reversal of the gradation reversal and gradation controlcircuit 29 is instantly changed by the light amount sensor 44, but thegradation control thereof is performed by changing the gradation controlshown in FIG. 14 and FIG. 15 gradually with a lapse of time when theauxiliary light source 9 is turned on and turned off, thereby enabling asmooth switching of the gradation. This becomes a very effective meanswhen the amount of light in the external environment is abruptly changedduring moving by a car or the like.

INDUSTRIAL APPLICABILITY

The liquid crystal display device according to the present invention canrealize a display with excellent visibility which is bright enoughwithout reversal of brightness and darkness of the display during boththe reflection display state by the external light and the transmissiondisplay state by turning on the auxiliary light source. It is possibleto increase contrast of the display and to improve the viewing anglecharacteristic.

Moreover, it is possible to perform a color display and also to make thegradation adequate in correspondence with brightness.

For instance, a brightness of the environment where the liquid crystaldisplay device is used by the external light source is detected by thelight amount sensor, and correction of the gradation signal in such amanner that the halftone thereof is deviated in the bright direction orthe dark direction is performed by the detecting signal of the lightamount sensor, thereby making it possible to improve the display qualityalso in the case where the reflection display is performed.

Accordingly, through the use of the liquid crystal display device for atimepiece such as a wristwatch or the like and for a display device ofvarious kinds of portable information processing devices, the visibilitythereof is substantially improved.

What is claimed is:
 1. A liquid crystal display device, comprising: aliquid crystal cell made by disposing a first substrate provided withscanning electrodes and a second substrate provided with data electrodesin such a manner that the scanning electrodes and the data electrodesare oppositely disposed to each other with a predetermined spacetherebetween, and a liquid crystal layer being filled between the firstsubstrate and the second substrate, wherein the second substrate of saidliquid crystal cell is disposed on the visible side, a polarizing filmis disposed on the side of each face of the first substrate and secondsubstrate opposite the face contacting the liquid crystal layer, whereinthe polarizing film disposed on the first substrate side is areflection-type polarizing film which transmits light linearly polarizedin a direction parallel to a transmission axis thereof and reflectslight linearly polarized in a direction parallel to a reflection axisthereof orthogonal to the transmission axis, an auxiliary light sourceis provided on the side of the reflection-type polarizing film oppositethe face on the first substrate side, and wherein means for reversing amagnitude relation of a voltage applied to the liquid crystal layerbetween the auxiliary light source being turned on and being turned offis provided.
 2. The liquid crystal display device according to claim 1,wherein a gradation signal is applied to the liquid crystal layer fordisplaying half tone and the means for reversing a magnitude relation ofa voltage applied to the liquid crystal layer between the auxiliarylight source being turned on and being turned off is a circuit forreversing a magnitude relation of a gradation signal applied to theliquid crystal layer.
 3. The liquid crystal display device according toclaim 2, wherein the gradation signal is set such that the halftone isdeviated in a direction where the reflectance is large when theauxiliary light source is turned off, and the halftone is deviated in adirection where the transmittance is small when the auxiliary lightsource is turned on.
 4. The liquid crystal display device according toclaim 1, wherein a scattering film having light scattering properties isprovided between the first substrate and the reflection-type polarizingfilm.
 5. The liquid crystal display device according to claim 4, whereinthe scattering film adheres to the reflection-type polarizing film. 6.The liquid crystal display device according to claim 1, wherein a lightabsorbing layer for transmitting part of light is provided between thereflection-type polarizing film and the auxiliary light source.
 7. Theliquid crystal display device according to claim 6, wherein a scatteringfilm having light scattering properties is provided between thereflection-type polarizing film and the light absorbing layer.
 8. Theliquid crystal display device according to claim 7, wherein thescattering film adheres to the reflection-type polarizing film.
 9. Theliquid crystal display device according to claim 7, wherein thescattering film is a plastic film in which asperities are formed on thefront face thereof or a plastic film in which beads with differentrefractive indexes are dispersed and is bonded to the rear face of thereflection-type polarizing film with an adhesive.
 10. The liquid crystaldisplay device according to claim 7, wherein a gap is provided betweenthe scattering film and the light absorbing layer.
 11. The liquidcrystal display device according to claim 6, wherein the light absorbinglayer is made of a printed layer having opening portions with a largetransmittance and absorbing portions with a small transmittance.
 12. Theliquid crystal display device according to claim 11, wherein the lightabsorbing layer having the opening portions forms a grid form in whichthe opening portions and the absorbing portions are arranged regularlyand the printed layer forming the absorbing portions is made of a thickfilm for absorbing external light by the thickness thereof when anincident angle of the external light becomes large.
 13. The liquidcrystal display device according to claim 6, wherein the light absorbinglayer has a plurality of opening portions or portions having atransmission characteristic at a pixel portion.
 14. A liquid crystaldisplay device, comprising: a liquid crystal cell made by disposing afirst substrate provided with scanning electrodes and a second substrateprovided with data electrodes in such a manner that the scanningelectrodes and the data electrodes are oppositely disposed to each otherwith a predetermined gap therebetween, and a liquid crystal layer beingfilled between the first substrate and the second substrate, wherein thesecond substrate of said liquid crystal cell is disposed on the visibleside, wherein an absorption-type polarizing film is disposed on the sideof a face of the second substrate opposite the face contacting theliquid crystal layer, and a cholesteric liquid crystal polymer film isdisposed on the side of a face of the first substrate opposite to theface contacting the liquid crystal layer respectively, wherein anauxiliary light source is disposed on the side of a face of thecholesteric liquid crystal polymer film opposite the face on the firstsubstrate side, and wherein means for reversing a magnitude relation ofa voltage applied to the liquid crystal layer between the auxiliarylight source being turned on and being turned off is provided.
 15. Theliquid crystal display device according to claim 14, wherein a gradationsignal is applied to the liquid crystal layer for displaying halftone,and the means for reversing a magnitude relation of a voltage applied tothe liquid crystal layer between the auxiliary light source being turnedon and being turned off is a circuit for reversing a magnitude relationof a gradation signal applied to the liquid crystal layer.
 16. Theliquid crystal display device according to claim 5, wherein thegradation signal is set such that the halftone is deviated in adirection where the reflectance is large when the auxiliary light sourceis turned off and the halftone is deviated in a direction where thetransmittance is small when the auxiliary light source is turned on. 17.The liquid crystal display device according to claim 14, wherein aretardation film is disposed between the second substrate and theabsorption-type polarizing film, and a quarter-wavelength film isdisposed between the first substrate and the cholesteric liquid crystalpolymer film respectively.
 18. The liquid crystal display deviceaccording to claim 14, wherein a light absorbing layer for transmittingpart of light is provided between the cholesteric liquid crystal polymerfilm and the auxiliary light source.
 19. The liquid crystal displaydevice according to claim 18, wherein the light absorbing layer is aprinted layer having transparency so that the light absorbing layer as awhole transmits part of light.
 20. A liquid crystal display device,comprising: a liquid crystal cell made by disposing a first substrateprovided with scanning electrodes and a second substrate provided withdata electrodes in such a manner that the scanning electrodes and thedata electrodes are opposed to each other with a predetermined gaptherebetween, a liquid crystal layer being filled between the firstsubstrate and the second substrate, and a first color filter beingprovided on the first substrate, wherein the second substrate of saidliquid crystal cell is disposed on the visible side, wherein anabsorption-type polarizing film is disposed on the side of a face of thesecond substrate opposite the face contacting the liquid crystal layer,and a reflection-type polarizing film is disposed on the side of a faceof the first substrate opposite to the face contacting the liquidcrystal layer respectively, wherein an auxiliary light source isdisposed on the side of a face of the reflection-type polarizing filmopposite to the face on the first substrate side with a second colorfilter therebetween, and wherein means for reversing magnitude relationof a voltage applied to the liquid crystal layer between the auxiliarylight source being turned on and being turned off is provided.
 21. Theliquid crystal display device according to claim 20, wherein ascattering film having light scattering properties is provided betweenthe first substrate and the second color filter.
 22. The liquid crystaldisplay device according to claim 21, wherein the scattering film is aplastic film in which asperities are formed on the front face thereof ora plastic film in which beads with different refractive indexes aredispersed.
 23. The liquid crystal display device according to claim 21,wherein each of the first color filter and the second color filter ismade of red, green, and blue color filters.
 24. The liquid crystaldisplay device according to claim 23, wherein the first color filter andthe second color filter are provided on one face side of the firstsubstrate and on the other face side respectively and disposed in such amanner that the color filters of the same color overlap one another withthe first substrate therebetween in almost the same areas.
 25. Theliquid crystal display device according to claim 20, wherein means forcontrolling a voltage applied to the liquid crystal layer is provided tovary brightness of a display of a halftone in accordance with brightnessof an external environment.